Los Angeles unified school system said hackers attacked during Labor Day weekend.
The district called the cyber-attack a "serious disturbance to our system's infrastructure," but authorities don't foresee severe difficulties with teaching or transportation and meals.
Classes were planned to begin as normal Tuesday, the district stated in a statement.
The criminals seem to have targeted facilities systems, which include private-sector contractor payments that are publicly accessible via records requests, authorities said.
Authorities think the assault originated worldwide and have identified three possible nations, but LAUSD Superintendent Alberto Carvalho won't identify which ones.
Ransomware is attacking the education sector more than previously. In August and September 2021, 57% of ransomware instances reported to the FBI affected K-12 schools.